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TROPICAL STORM CHANTAL DISCUSSION NUMBER 11
NATIONAL WEATHER SERVICE MIAMI FL
5 AM EDT SAT AUG 18 2001
CHANTAL IS A BIT TRICKY TO LOCATE THIS MORNING. A HURRICANE HUNTER
AIRCRAFT IN THE STORM PRIOR TO 06Z INDICATED THE WIND FIELD WAS
DISTORTED DUE TO THE RAPID MOTION AND THAT THE CENTER WAS HARD TO
FIND. A RECENT TRMM OVERPASS HAS FURTHER COMPLICATED MATTERS...
SUGGESTING THAT A BROAD LOW LEVEL CENTER IS NORTH OF THE AIRCRAFT
FIXES...CURRENT SATELLITE FIXES...AND THE PRIMARY CONVECTION. THE
AIRCRAFT DID REPORT A 1003 MB PRESSURE AND 1500 FT WINDS OF 73 KT.
THE WINDS MAY HAVE BEEN RELATED TO MESOSCALE CONVECTIVE EFFECTS...SO
THE INTENSITY FOR THIS PACKAGE WILL BE SET TO A MORE CONSERVATIVE
50 KT.
EVEN WITH THE ABOVE DIFFICULTIES...CHANTAL APPEARS TO BE MOVING A
LITTLE MORE WESTWARD THAN PREVIOUSLY...275/20. THE STORM IS
CURRENTLY TO THE SOUTH OF A STRONG DEEP-LAYER RIDGE...AND LARGE-
SCALE MODELS INDICATE THIS SHOULD CONTINUE FOR 24-36 HR. THIS
SHOULD KEEP CHANTAL ON A GENERAL WEST TO WEST-NORTHWEST TRACK.
THE MODELS FORECAST THE RIDGE TO WEAKEN AFTER 36 HR AS A MID/UPPER
LEVEL TROUGH DEVELOPS OVER THE EASTERN U.S....AND NHC HURRICANE
GUIDANCE RESPONDS TO THIS BY DIVERGING. THE NOGAPS AND GFDL MODELS
KEEP CHANTAL MOVING GENERALLY WEST-NORTHWESTWARD TOWARD THE YUCATAN
PENINSULA...WHILE THE AVN...BAMD...AND LBAR TURN THE STORM
NORTHWESTWARD TOWARD WESTERN CUBA OR THE YUCATAN CHANNEL. THE
GFDN IS AN EXTREME WEST OUTLIER...TAKING CHANTAL INTO THE PACIFIC
BY 72 HR. WHILE THIS IS UNLIKELY...IT COULD HAPPEN IF CHANTAL
STAYS FAR ENOUGH SOUTH TO MISS CONNECTIONS WITH THE TROUGH. THE
OFFICIAL FORECAST IS SLIGHTLY SOUTH OF THE PREVIOUS TRACK IN THE
MIDDLE OF THE GFDL...VICBAR...NHC98 AND CLIPER MODELS.
CHANTAL CONTINUES TO GENERATE STRONG CONVECTION TO THE SOUTH OF
THE CENTER AND CONTINUES TO SHOW GOOD ANTICYCLONIC OUTFLOW.
CONDITIONS APPEAR FAVORABLE FOR ADDITIONAL STRENGTHENING SHOULD
THE STORM EVER GET ITS ACT TOGETHER. THE INTENSITY FORECAST CALLS
FOR CHANTAL TO BECOME A HURRICANE IN 24 HR AND REACH CATEGORY 2
STATUS AS IT APPROACHES THE YUCATAN PENINSULA. IT IS NOTABLE
THAT THE HURRICANE RESEARCH DIVISION'S EXPERIMENTAL TECHNIQUE FOR
PREDICTION RAPID INTENSIFICATION REALLY LIKES CHANTAL...SUGGESTING
THAT IT COULD BE SIGNIFICANTLY STRONGER THAN CURRENTLY FORECAST
ONCE IT FINALLY CONSOLIDATES.
THE GOVERNMENT OF JAMAICA HAS ISSUED A HURRICANE WARNING FOR THE
ISLAND. WHILE THE CURRENT FORECAST TRACK AND WIND RADII WOULD
KEEP HURRICANE CONDITIONS SOUTH OF THE ISLAND...AND TRACK TO THE
RIGHT OF THE FORECAST TRACK WOULD BRING HURRICANE CONDITIONS TO THE
ISLAND.
FORECASTER BEVEN
FORECAST POSITIONS AND MAX WINDS
INITIAL 18/0900Z 14.8N 71.3W 50 KTS
12HR VT 18/1800Z 15.3N 74.2W 60 KTS
24HR VT 19/0600Z 16.1N 77.4W 70 KTS
36HR VT 19/1800Z 17.0N 80.1W 75 KTS
48HR VT 20/0600Z 17.8N 82.6W 80 KTS
72HR VT 21/0600Z 19.5N 87.0W 85 KTS
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